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Transcript
Chapter 6 The Earth Our Earth is a very special place. Seeds Of Life Thank you liquid water! Not too hot, not too cold! Composition of the Earth’s primitive atmosphere • First atmosphere (4.4-4.6 billion years ago): hydrogen and helium • Second atmosphere (4.4-4.0 billion years ago): water vapor, ammonia, and methane • Third atmosphere (3.3-4.0 billion years ago): 98% carbon dioxide, 2% water vapor and nitrogen Volcanic eruptions and impacts from asteroids and comets may have created our primitive atmosphere Thank you bacteria! Cyanobacteria helped to produce oxygen and remove carbon dioxide Current atmosphere (present day-3.3 billion years ago): 78% nitrogen and 21% oxygen Thank you ozone layer! • Oxygen was important for producing ozone since ozone is O3 • The ozone formed before early life could move from the oceans onto dry land • The ozone protects the surface from hazardous UV radiation from the Sun Chlorofluorocarbons (CFC’) • Our Ozone is destroyed by CFCs which are chemicals produced by refrigeration, air conditioners, foam and aerosols • They are very efficient at removing ozone • Ozone slowly replenishes itself as it is created from sunlight and lightning Thank you magnetic field! The Earth’s magnetic field shields us from the stream of charged particles from the Sun and cosmic ray particles from space Aurora Earth is the only terrestrial planet to have a significant magnetic field! To have a significant magnetic field, the planet must: 1. Be a fast rotator- Earth takes 24 hours to rotate 2. Liquid metallic interior- Earth has outer molten iron core Earth’s interior consists of a rocky mantle and an iron rich core Differentiation Plate Tectonics Earth’s surface is composed of about twelve major plates which slowly move relative to one another Collision of two plates separation forms mountains The San Andreas Fault Plate tectonics is driven by convective currents in Earth’s mantle Continental Drifting Plate tectonics produced major changes to the Earth’s surface over the past 200 million years Earth in the Future